The present invention relates to a urological resectoscope.
A resectoscope of a different kind is disclosed in the German patent 2,428,000 and shown in its FIG. 8. The author of this document is Dr. Iglesias who therein disclosed the first permanently rinsing resectoscope. Separate feed and drain ducts to rinse the region of the field of view are assured by the double-stem design, and as a result resecting with a clear view shall be assured for a long time.
As regards the latter resectoscopes, resecting entails first distally advancing the cutting loop and then retracting it while cutting through the tissue. In order to cut off cleanly the tissue strips, the cutting loop must cut against the distal stem rim constituting one cutting edge. The stem will be strongly heated in this process. Accordingly, the distal rim zone of the stem must consist of a high-temperature resistant material, which furthermore shall be electrically insulating in order to preclude hf contact with the surgeon holding the resectoscope.
In the design disclosed in the above reference, the shading (per US standard) denotes the outer stem that constitutes the cutting edge for the non-conducting cutting loop. However, substantial costs and handling difficulties are incurred by making the entire outer stem of plastic or ceramic.
Accordingly the German Gebrauchsmuster 7,426,959 proposed a design of the above species wherein both stems are metallic and a separate insulating shell constituting the cutting edge is used. In this design the insulating shell is affixed to the inner stem. This design has become the present-day standard. This design entails a slight drawback, which however becomes significant in medical use.
The tubular insulating shell constitutes the end element of the inner stem. Because of the required annular space between the stems, the diameter of the other stem is larger than that of the insulating shell. On the other hand the insulating shell""s inside diameter determines the maximum size of the cutting loop. As a result, this design entails an outside diameter substantially larger than that of the cutting loop.
The surgeon desires the largest possible cutting loop so as to be able to slice off the biggest strips as fast as possible. On the other hand, he desires a resectoscope of minimal outside diameter in order not to unduly stretch the tissue duct through which the resectoscope is being inserted, usually the human urethra, which would entail traumatic tissue tearing. The differential of the inside insulating shell diameter and the outside outer stem diameter therefore should be minimized. However, the resectoscope of the state of the art gave rise to the above cited problems.
An objective of the present invention is to create a resectoscope of the above kind wherein the differential of the inside insulating shell diameter and the outside outer stem diameters may be reduced.
As regards the invention, and contrary to the state of the art, the insulating shell is not affixed to the inner stem but instead to the outer stem. In particular, the insulating shell may exhibit the same diameter as the outer stem. In this configuration, the inner stem may be radially sufficiently spaced from the outer stem to subtend a return flow duct of large volume. The diameter differential of the inner insulating shell stem and outer stem thereby can be reduced to the insulating shell""s wall thickness. Without incurring further drawbacks, this design, when applied to otherwise conventional resectoscopes, allows reducing the outside diameter by about 1 mm, or, with the outside diameter remaining constant, the loop diameter may be enlarged by about 1 mm. Considering that to-date decades have been spent in attaining reductions of several tenths of a mm only, the invention amounts to a gigantic step forward.
Moreover, in this design, the cutting-loop diameter shall not be constrained by the inside diameter of the inner stem. The cutting loop is conventionally supported by prongs present at the distal end of the electrode support. The prongs are spaced apart as much as possible in order to reliably hold in place the cutting loop. However, to create a large-volume return flow duct, the inside diameter of the inner stem must be small. In accordance with the present invention, an inner stem subtending a small volume allows creating a large-volume return flow duct, yet the prongs running in outwardly convex grooves of the inner stem may be substantially apart from each other.
In further accordance with the present invention, the inner stem may distally project by its distal rim beyond the insulating shell and rest by its inside in sealing manner against said insulating shell. However, the inner stem also may abut the proximal insulating shell rim in order to implement thereby an especially smooth transition and in order not to restrict the free length of the insulating shell required for the cutting loop""s excursion.
As regards modern resectoscopes, their two stems rest in mutually rotatable manner at their proximal affixation site in the manner shown in the German patent disclosure DE 410 1472 C2. When continuously rotating the resectoscope in order to allow cutting at different angular positions, for instance as required especially in prostate resection, the invention attains the advantage that, while the cutting loop and the inner stem are being rotated, the outer stem may rest free of rotation relative to and in the urethra and thus remain in the urethra without causing trauma to it. This feature offers the further advantage that, when using the design of the German Gebrauchsmuster 74 26959 for the distal stem zones having an insulating body mounted to the inner stem and in the form of a slanted beak, the beak shape rotates together with the cutting loop and therefore provides a constant cutting edge. The beveled beak shape provides hydrodynamic advantages.
On the other hand, if the insulating shell is firmly affixed to the outer stem and if the cutting loop is being rotated, then initially only a straight-cut, distal terminal edge of the insulating shell may be selected because it alone shall assure constant cutting conditions in all directions of rotation. However, according to a further feature o the invention, the insulating shell still is mounted on the outer stem, but in a rotatable manner relative to it, and it is linked to the inner stem to rotate with latter. When the inner stem together with the cutting loop is being rotated, the cutting loop is therefore also rotated. This design offers the advantage that the insulating shell now can be fitted with the desired beveled beak shape.
In further accordance with the present invention, if the distal inner-stem rim is configured obliquely, there will be zones of the distal edge that are distally farther and zones that are closer to the proximal end of the instrument. The annular space subtended between the inner and outer stems are more distal at the more distal zones and orifices may be provided at the more distal zones to aspirate distally far out liquid. This feature is advantageous in case the resectoscope outer stem is tightly enclosed almost to its distal end. As a result and even under unfavorable conditions, unhampered permanent rinsing may still be assured. Advantageously, the bevel of the distal inner-stem rim may be selected such that the rim is more proximal within the circumferential zone that encloses the central zone of the cutting loop, whereby at that location the cutting loop can be retracted enough, namely as far as into a zone opposite which there are already suction orifices.